We tend to believe that we have a natural instinct for the truth but the web has many inaccuracies that are commonly held to be factual. We can follow the old journalistic principle of getting at least two reliable sources for important pieces of information, but much of the internet is a mash up of other bits of the internet. The resulting multiplicity of sources might suggest a breadth of knowledge but in reality if a factoid is convincing enough it can spread.

Wikipedia is amongst the most reliable of sources because the content is genuinely the result of multiple entries, sometimes hundreds of them. Even Wikipedia has been guilty of significant errors – often the result of malicious editing. Prominent US journalist John Seigenthaler was incorrectly named as a suspect in the assassinations of both President John F Kennedy and his brother, Robert for example. The false information was the work of a man called Brian Chase, who said he was trying to trick a colleague at work.

A common error is that of the false obituary. It has even been know for false obituaries to be published on on separate occasions. Pre-written obituaries of entertainer Bob Hope were accidentally released on news web sites on two occasions and Pope John Paul II was the recipient of three separate reports of his demise. Other widely duplicated falsehoods on the internet include a report that Barack Obama is a muslim and that Bill Gates is giving away his fortune. This sort of widely distributed misconception is not the preserve of the Internet, for example the Great Wall of China Is not in fact nor ever has been, visible from the Moon, but the internet provides a distribution network that spreads these inaccuracies more widely and more quickly.

It is not just facts that are manipulated and distorted, the prevalence of powerful image manipulation tools means that photographs can not necessarily be trusted either. Even the celebrated news agency Reuters came under fire for this when in 2006 it published doctored images of an Israeli air strike in Beirut.

Stephen Fry, Andy Murray and Jonathan Ross are amongst the growing band of celebrities on Twitter, but how do we know that it is really them and not just a fan of even a member of their celebrity entourage posting, purely for publicity?

There have been a host of examples of fake Twitterers and bloggers. For over a year a blog ran under the moniker “Fake Steve” or FSJ, a fake Steve Jobs blog that in some months attracted almost a million visitors including the real Steve Jobs and apparently the real Bill Gates too.

The business of revealing a celebrity Twitter as a fake in the title is an established phenomenon (at the time of writing the newly reinstated Twitter search facility revealed over 200 of these). The bigger issue is the ease with which anyone can register a name and become a twit imposter.

So how do we tell if the celebrity on Twitter is the real deal? There are some tests that we can apply:

1 The Authentic Voice. Does it feel real? This can be an acid test in itself. Whilst it might be possible to adopt a persona for a few tweets it is very difficult to sustain over time. We should trust our instincts (but not rely on them solely). Whilst some tweets feel like celebrity publicists at work (@BritneySpears admits as much) if you follow @Andy_Murray it doesn’t feel like it could be anyone else.

2. The Official Website. Stephen Fry, who is no slouch when it comes to the social web, fed his Twitter stream to his official web-site. Voila, instant validation, so it’s worth checking.

3. The Fourth Estate. Traditional media channels and established journalists remain vital to news and communications because they set the bar for accuracy and authority (a subject worthy of much further discussion). When I openly asked on Twitter if @wossy was the real Jonathan Ross two journalists pointed me in the direction of established news source confirming it. Check them out.

4. Ask. Put the question on Twitter either directly or to the Twittersphere. It is the social web after all and you might get the confirmation that you need.

The social web of its nature creates margins for doubt and error but if you apply these tests you should fairly quickly be able to separate the glam from the sham.